Lohan will romance Sheen's character Charlie Goodson after becoming one of his therapy patients.
Sheen and Lohan worked together on "Scary Movie 5" and have struck up a friendship. Last year the actor reportedly gave her $100,000 to pay off a tax debt.
Sheen also offered to pay for a gown she wore to an amFAR event earlier this month. Lohan has since been accused of ruining the $1,750 dress she borrowed for it. When she returned it to the fashion house the bottom of the dress had been hacked off.